What do sea otters eat?
Sea otters are known for being playful and frisky. They are serious eaters, however! A major part of a sea otter's diet are echinoderms, such as sea urchins. They manage to eat the soft part of the sea urchins while avoiding the huge sea urchin spines.
Echinoderms are important in many ways. They play many key roles in the ecosystem. They also are a source of food and medicine for humans.
Echinoderms play many important roles in the ecosystem. Sand dollars and sea cucumbers burrow into the sand, providing more oxygen at greater depths of the sea floor. This allows more organisms to live there. In addition, starfish prevent the growth of algae on coral reefs. This allows the coral to filter-feed more easily. And many sea cucumbers provide a habitat for parasites such as crabs, worms, and snails.
Echinoderms are also an important step in the ocean food chain. Echinoderms are the staple diet of many animals, including the sea otter. On the other hand, echinoderms eat seaweed and keep its growth in check. Their role as grazers on the sea floor, therefore, is very important. Recently, some marine ecosystems have been overrun by seaweed. Excess seaweed can destroy entire reefs. Scientists believe that the extinction of large quantities of echinoderms has caused this destruction (Figure below).
A large die-off of the sea urchin Diadema antillarum in the Caribbean Sea coincided with increases in algal growth in some areas but not others.
Echinoderms as Food
In some countries, echinoderms are considered delicacies. Around 50,000 tons of sea urchins are captured each year for food. They are consumed mostly in Japan, Peru, and France. Sea cucumbers are considered a delicacy in some southeastern Asian countries.
Echinoderms as Medicine
Echinoderms are also used as medicine and in scientific research. For example, some sea cucumber toxins slow down the growth rate of tumor cells, so there is an interest in using these in cancer research.
Echinoderms in Farming
The external covering of echinoderms is used as a source of lime by farmers in some areas where limestone is unavailable. Lime is added to the soil to allow plants to take up more nutrients. About 4,000 tons of the animals are used each year for this purpose.
lime: A white substance added to the soil to reduce acidity and improve fertility.
sea urchin: Echinoderm with a round, soft body enclosed in a shell covered with long spines.
- Echinoderms are an important part of the ocean food chain, keeping seaweed in check as grazers and serving as food sources for animals like otters.
- Echinoderms are used as food, medicine, and a source of lime for farmers.
Use the resource below to answer the questions that follow.
- What characteristics of the sea cucumbers inspired scientists to use them to develop new polymers?
- Why do scientists feel these new polymers may be useful for medical implants?
- How are echinoderms important to the ecosystem?
- How are echinoderms important to humans?